Semiconductor chip stack and manufacturing method thereof

ABSTRACT

A semiconductor chip stack includes a first chip and a second chip. The first chip includes a first circuit formed in the first chip with a first integration density, and the second chip includes a second circuit in the second chip with a second integration density smaller than the first integration density. The first chip further includes at least a through-silicon via formed therein for electrically connecting the first chip and the second chip.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor chip stack andmanufacturing method thereof, and more particularly, to a semiconductorchip stack having through-silicon via (TSV) and manufacturing methodthereof.

2. Description of the Prior Art

Integrated circuit (IC) products are constructed by chips that arefabricated by conventional semiconductor manufacturing processes. Theprocesses to fabricate a chip start with a wafer: a plurality of regionsis defined on a wafer. Then, conventional semiconductor manufactureprocesses such as deposition, photolithography, etching or planarizationare performed to form the desired circuit trace(s) and followed byseparating each region to form a plurality of chips. Chips are packagedto form a chip package; and the chip package is attached on a board suchas a printed circuit board (PCB). It is also well-known that the chip iselectrically connected to pins on the PCB and thus each of the programson the chip can be performed.

Pursuing thinner and lighter IC products, the semiconductor industriesalways tries to reach the limits to the process miniaturization, and todevelop different package technologies. For example, flip-chip (FC)technology, multi-chip package (MCP) technology, package on package(PoP) technology, package in package (PiP) technology are developed tostack the chips or packages in three dimensions, therefore density ofthe semiconductor devices per unit volume is increased. In recent years,a “through-silicon via (TSV)” technique is further developed to improveinterconnections between chips in the package so as to increase thepackage efficiency.

Please refer to FIGS. 1-2, which are schematic drawings of aconventional IC product. Left of FIG. 1 is a schematic drawing of awafer; and right of FIG. 1 is an enlarged view of a region in the waferof FIG. 1. As shown in FIG. 1, IC product is fabricated by providing awafer 100 having a plurality of regions 102 defined thereon. Thendifferent semiconductor processes are performed to the wafer 100, andthe required semiconductor devices are formed in each region 102. Theregions are separated to form chips possessing a specific function. Asshown in the right of FIG. 1, when a region 102 is predetermined to be adynamic random access memory (DRAM) chip, memory core array is formed ina center region of each region 102, and a sub-region 104 with a highdevice integration density is obtained. In the meantime, a peripheralcircuit or I/O pads are formed in a peripheral region of each region102, and a sub-region 106 with a low device integration density isobtained. Therefore each region 102 includes both of the sub-region 104of high integration density and the sub-region 106 of low integrationdensities. When the regions 102 of different wafers 100 arepredetermined to form chips possessing different specific function, suchas analog chip, flash memory chip, or CPU chip, the region 102 is formedto include many sub-regions 104/106 of high or low integrationdensities.

After separating the regions 102 to obtain the chips, the prior art isto stack and package the chips with different specific function, thus asemiconductor chip package 110 is obtained. As shown in FIG. 2, theconventional chip package 110 includes a carrier 112, a CPU chip 114 a,a DRAM chip 114 b, a flash memory chip 114 c, and an analog chip 114 dupwardly stacked on the carrier 112. And the active surfaces of eachchip in the package 110 are electrically connected by TSV 116.

As mentioned above, the conventional chips respectively possess onespecific function, and each chip comprises kinds of semiconductordevices in the sub-regions with different integration densities.However, the devices are formed by the same processes. For example, tocomply with the process requirement for fabricating the devices withhigh integration density, high-grade semiconductor processes areperformed to the wafer even though the devices with low integrationdensity need no such high-grade semiconductor processes. In fact,devices with different integration densities require processes ofdifferent grades. Therefore, wastes of cost and source have been causedwhen the semiconductor processes are performed to the wafer 100.Consequently, a semiconductor chip stack and manufacturing method thatis able to improve process efficiency and to lower the cost is still inneed.

SUMMARY OF THE INVENTION

It is therefore a primary objective of the present invention to providea semiconductor chip stack and manufacturing method that is able toimprove process efficiency and to lower the cost.

According to the claimed invention, a semiconductor chip stack isprovided. The semiconductor chip stack comprises a first chip having afirst circuit of a first integration density formed therein and a secondchip having a second circuit of a second integration density formedtherein, the second integration density is smaller than the firstintegration density. The first chip further comprises at least a TSVformed therein for electrically connecting the first chip and the secondchip.

According to the claimed invention a method of manufacturing asemiconductor chip stack is provided. The method comprises steps ofproviding a circuit layout of a function device, the circuit layoutfurther comprising a first device layout and a second device layout, andan integration density of the first device layout is larger than anintegration density of the second device layout; defining a plurality offirst chip regions on a first wafer and forming the first device layoutin each first chip region; defining a plurality of second chip regionson a second wafer and forming the second device layout respectivelycorresponding to the first device layout in each second chip region;respectively forming a plurality of first TSVs in the first wafer forelectrically connecting the first device layout and the second devicelayout; and respectively cutting the first wafer and the second wafer toform a plurality of first chips and a plurality of second chips.

According to the semiconductor chip stack and manufacturing methodprovided by the present invention, circuit layouts of one specificfunction device are respectively formed on different chips according tothe integration density, and then the chips are electrically connectedby TSV technology. Thus the desired specific function is obtained. Sincedifferent chips are to be formed with different integration densities,processes of high-grade or low-grade is performed to form the chipsaccording to its integration density. Therefore the process efficiencyis improved while the cost is lowered.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-2 are schematic drawings of a conventional IC product;

FIG. 3 is a flowchart illustrating a method of manufacturing asemiconductor chip stack provided by a first preferred embodiment of thepresent invention;

FIGS. 4-6 are schematic drawings illustrating the first preferredembodiment;

FIG. 7 is a schematic drawing illustrating a second preferred embodimentof the present invention;

FIG. 8 is a flowchart illustrating a method of manufacturing asemiconductor chip stack provided by a third preferred embodiment of thepresent invention; and

FIGS. 9-10 are schematic drawings illustrating the third preferredembodiment.

DETAILED DESCRIPTION

Please refer to FIGS. 3-6, FIG. 3 is a flowchart illustrating a methodof manufacturing a semiconductor chip stack provided by a firstpreferred embodiment of the present invention, and FIGS. 4-6 areschematic drawings illustrating the first preferred embodiment. As shownin FIG. 3, the method of manufacturing a semiconductor chip stackprovided by the first preferred embodiment includes steps of:

Step 200: providing a circuit layout of a function device, the circuitlayout further comprising a first device layout 312 and a second devicelayout 412.

In the first preferred embodiment, the function device includes a memorydevice such as a dynamic random access memory (DRAM) or a NAND-typenon-volatile memory. It is well-known to those skilled in the art thatthe circuit layout of the DRAM or the NAND-type non-volatile memoryfurther includes a memory core array layout which comprises higherintegration density, and a peripheral circuit layout having logiccircuits, electrostatic discharge (ESD) protection devices and I/O pads,which comprises lower integration density. In the first preferredembodiment, the first device layout is the memory core array layout ofhigher integration density and the second device layout is theperipheral circuit layout of lower integration density.

Please refer to FIGS. 3-4. After Step 200, Step 210 and Step 212 areperformed:

Step 210: defining a plurality of first chip regions 310 on a firstwafer 300, and forming the first device layout 312 in each first chipregion 310;

Step 212: defining a plurality of second chip regions 410 on a secondwafer 400, and forming the second device layout 412 in each second chipregion 410;

It is noteworthy that Step 210 and Step 212 are performed to form thefirst device layout 312 and second device layout 412 on the first wafer300 and the second wafer 400 respectively, therefore Step 210 and Step212 can be performed simultaneously or sequentially by the relatedsemiconductor processes. Since the integration densities of the firstdevice layout 312 and the second device layout 412 are different, thefirst device layout 312 with higher integration density is formed on thefirst wafer 300 by high-grade processes, and the second device layout412 with lower integration density is formed on the second wafer 400 bylow-grade processes.

Please refer to FIG. 3 and FIG. 5. After performing the semiconductorprocesses, Step 220 and Step 230 are performed:

Step 220: forming a plurality of first TSVs 330 and a plurality ofsecond TSVs 430 respectively in the first wafer 300 and the second wafer400.

Step 230: respectively cutting the first wafer 300 and the second wafer400 to form a plurality of first chips 320 and a plurality of secondchips 420.

According to Step 220 of the first preferred embodiment, the first TSVs330 (shown in FIG. 6) are formed in the first chip region 310 and thesecond TSVs 430 (also shown in FIG. 6) are formed in the second chipregion 410. It is well-known to those skilled in the art that TSVprocess can be performed at different time point among the wholesemiconductor processes or the packaging processes. The TSV process usedto form the first TSVs 330 and the second TSVs may be divided into twotypes, namely the via-first or the via-last process. The via-firstprocess is performed before or after forming CMOS, or after theback-end-of-line process while the via-last process is performed in thepackaging process. Therefore the Step 220 can be performed in Step210/212, after Step 210/212, or after Step 230 depending on the processrequirement.

According to Step 230, the obtained first chip 320 and the second chip420 respectively comprises the first device layout 312 and the seconddevice layout 412. In other words, the first chip 320 comprises a memorycore array of a DRAM or an NAND-type non-volatile memory while thesecond chip 420 comprises a peripheral circuit of the aforementionedmemory, such as logic circuits, ESD protection devices and I/O pads.Thus, the second chip 420 serves as a global interface chip.

Please refer to FIG. 3 and FIG. 6. After individualizing the first chip320 and the second chip 420, Step 230 is performed:

Step 230: stacking the first chip 320 and the second chip 420 on acarrier 502.

As shown in FIG. 6, a packaging process is performed: the first chip 320and the second chip 420 are stacked on the carrier 502 and packaged toform a semiconductor chip 500. Although the second chip 420 ispositioned between the first chip 320 and the carrier 502 in FIG. 6, itis easily realized that the structural relationship between the firstchip 320 and the second chip 420 is not limited to this.

According to the first preferred embodiment, the provided semiconductorchip stack 500 comprises a first chip 320 having a first circuit 312 ofa first integration density formed therein and a second chip 420 havinga second circuit 412 of a second integration density formed therein. Thefirst chip 320 and the second chip 420 respectively comprise at least afirst TSV 330 and at least a second TSV 430. As mentioned above, thefirst circuit 312 comprises a core array of a memory such as DRAM orNAND-type non-volatile memory. The second circuit 412 is correspondingto the first circuit 312, and comprises logic circuits, ESD protectiondevices and I/O pads of the memory. Additionally, the first chip 320 andthe second chip 420 are not limited to comprise micro electro-mechanicalsystems (MEMS) structures.

As mentioned above, the core circuit and the peripheral circuit of afunction device such as DRAM or NAND-type non-volatile memory arerespectively fabricated on different chips according to its integrationdensities, and followed by packaging process. The chips respectivelycomprise the core circuit and the peripheral circuit are thenelectrically connected by TSVs to obtain the desired specific function.Since different chips are to be formed with different integrationdensities, high-grade or low-grade processes are performed to fabricatethe chips according to its integration density. Therefore the processefficiency is improved while the cost is lowered.

Please refer to FIG. 7, which is a schematic drawing illustrating asecond preferred embodiment of the present invention. Since steps in thesecond preferred embodiment are the same with the first preferredembodiment, those steps are omitted herein.

Please refer to FIG. 3. In Step 210, a plurality of first chip regions310 is defined on the first wafer 300, and each of the first chipregions 310 comprises a first device layout 312. Different from thefirst preferred embodiment, the first device layout 312 furthercomprises a core array of a first memory 312 a and a core array of asecond memory 312 b in the second preferred embodiment. The first memoryand the second memory can be different memories. For example, the firstmemory is a DRAM and thus the core array of a first memory 312 a is aDRAM core array; the second memory is a NAND-type non-volatile memoryand thus the core array of a second memory 312 b is a NAND-typenon-volatile memory core array. Furthermore, a plurality of chip regions410 are defined on the second wafer 400 and each of the second chipregions 410 comprises a second device layout 412. The second devicelayout 412 comprises a peripheral circuit 412 a having logic circuits,ESD protection devices and I/O pads of the DRAM and a peripheral circuit412 b having logic circuits, ESD protection devices and I/O pads of theNAND-type non-volatile memory.

Please refer to FIG. 3 and FIG. 6. In the second preferred embodiment,TSV processes for forming a plurality of first TSVs 330 (shown in FIG.6) and a plurality of second TSVs 430 (shown in FIG. 6) described inStep 220 are performed to the first wafer 300 and the second wafer 400in Step 210/212, after Step 210/212, or after Step 230. Then Step 230 isperformed: cutting the first wafer 300 and the second wafer 400 to forma plurality of first chips 322 and a plurality of second chips 422. Thefirst chip 322 and the second chip 422 are stacked on the carrier 502and packaged to form a semiconductor chip stack 500 as disclosed in Step230 and FIG. 6.

According to the second preferred embodiment, the first device layout312 formed on the first chip 322 comprises at least two different corecircuits 312 a/312 b, which are core arrays of the first memory and thesecond memory. And the peripheral circuits 412 a/412 b comprising logiccircuits, ESD protection devices and I/O pads of the first memory andthe second memory are formed in the second chip 422. The core circuitsand the peripheral circuits of function devices are respectivelyfabricated on different chips according to its integration densities,and followed by packaging process. The chips respectively comprise thecore circuit and the peripheral circuit are then electrically connectedby TSVs to obtain the desired specific function. According to the secondpreferred embodiment, the first chip 322 is fabricated to comprise corearrays of different memories, therefore function of the semiconductorchip 500 is enhanced. Since different chips are to be formed withdifferent integration densities, high-grade or low-grade processes areperformed to fabricate the chips according to its integration density.Therefore the process efficiency is improved while the cost is lowered.

Please refer to FIGS. 8-10, FIG. 8 is a flowchart illustrating a methodof manufacturing a semiconductor chip provided by a third preferredembodiment of the present invention, and FIGS. 9-10 are schematicdrawings illustrating the third preferred embodiment. Because Step 200,Step 210 and Step 212 are the same in the first and the third preferredembodiment, those steps and details are disclosed in FIGS. 3-5 and thusomitted herein.

Please refer to FIG. 8. According to the third preferred embodiment,Step 200 is performed to provide a circuit layout of a function device,and the circuit layout further comprises a first device layout 312 and asecond device layout 412. Then Step 202 and Step 214 are furtherperformed:

Step 202: providing a third wafer 600 having a plurality of third chipregions 610 defined therein.

Step 214: As shown in FIG. 9, forming a third device layout 612 in eachof the third chip region 610.

It is noteworthy that an integration density of the third device layout612 is larger than an integration density of the second device layout412. The first device layout 312 and the third device layout 612respectively comprises a core array of a first memory and a core arrayof a third memory. For example, the first device layout 312 is a DRAMcore array and the third device layout 612 is an NAND-type non-volatilememory core array. In a modification of the third preferred embodiment,both of the first device layout 312 and the third device layout 612comprise a core array of a first memory and a core array of a thirdmemory. For example, both of the first device layout 312 and the thirddevice layout 612 comprise a DRAM core array and an NAND-typenon-volatile memory core array. Thus the first device layout 312 and thethird device layout 612 comprise same memory core arrays. According tothe third preferred embodiment, the second device layout 412 comprises aperipheral circuit having logic circuits, ESD protection devices and I/Opads of the first memory and another peripheral circuit having logiccircuits, ESD protection devices and I/O pads of the third memory.

Step 222: forming a plurality of first TSVs 330, a plurality of secondTSVs 430 and a plurality of third TSVs 630 respectively in the firstwafer 300, the second wafer 400 and the third wafer 600.

Step 232: As shown in FIG. 5, cutting the first wafer 300, the secondwafer 400 and the third wafer 600 respectively to form a plurality offirst chips 320, a plurality of second chips 420 and a plurality ofthird chips 620.

According to Step 222, the first TSVs 330 are formed in the first chipregion 310, the of second TSVs 430 are formed in the second chip region410, and a plurality of third TSVs 630 are formed in the third chipregion 610 as shown in FIG. 10. As mentioned above, the TSV process canbe performed at different time point among the whole semiconductorprocesses and packaging processes, therefore Step 232 is performed inStep 210/212/214, after Step 210/212/214, or after Step 222.

Because the second device layout 412 comprises the peripheral circuitsof the first memory and the second memory, the second chip 420 serves asa global interface chip of the first chip 320 and the third chip 620.

Step 242: As shown in FIG. 10, stacking the first chip 320, the secondchip 420 and the third chip 620 on a carrier 512.

The first chip 320, the second chip 420 and the third chip 620 arestacked on the carrier 512 and packaged to form a semiconductor chipstack 510. In the third preferred embodiment, the second chip 420, whichservers as the global interface chip, is positioned between the firstchip 320 and the third chip 620, but not limited to this.

According to the third preferred embodiment, the provided semiconductorchip stack 510 comprises a first chip 320 having a core circuit 312 of afirst integration density formed therein, a third chip 620 having a corecircuit 612 of the first integration density formed therein, and asecond chip 420 having a peripheral circuit 412 of a second integrationdensity formed therein, and the peripheral circuit 412 is correspondingto the core circuits 312/612. The first chip 320, the second chip 420and the third chip 620 respectively comprise at least a first TSV 330,at least a second TSV 430 and at least a third TSVs 630. As mentionedabove, the core circuit 312/612 comprises core array of memories such asDRAM or NAND-type non-volatile memory while the peripheral circuit 314comprises logic circuits, ESD protection devices and I/O pads of theabovementioned memories. Additionally, the first chip 320, the secondchip 420 and the third chip 620 are not limited to comprise MEMSstructures.

It is noteworthy that the core arrays of higher integration density arefabricated in the first chip 320 and the third chip 620 and theperipheral circuit of lower integration density is fabricated in thesecond chip 420. Therefore the semiconductor processes of high-grade areperformed to the first chip 320 and the third chip 620 while thesemiconductor processes of low-grade are performed to the second chip420. Accordingly, process efficiency is improved.

According to the semiconductor chip stack and manufacturing methodprovided by the present invention, circuit layouts of one functiondevice are respectively form on different chips according to theintegration density, then the chips are electrically connected by FC,MCP, or preferably TSV technology. Thus the desired specific function isobtained. Since different chips are to be formed with differentintegration densities, processes of high-grade or low-grade is performedto form the chips according to its integration density. Therefore theprocess efficiency is improved while the cost is lowered. Furthermore,because TSV technology is adapted in the present invention, the providedmethod of manufacturing a semiconductor chip stack also can be used indifferent package technologies such chip-to-chip, chip-to-wafer orwafer-to-wafer processes.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention.

1. A semiconductor chip stack comprising: a first chip having a firstcircuit of a first integration density formed therein; and a second chiphaving a second circuit of a second integration density formed therein,the second integration density is smaller than the first integrationdensity; wherein the second circuit comprises logic circuits,electrostatic discharge (ESD) protection devices and I/O pads of a firstmemory of the first circuit; and the first chip further comprises atleast a through-silicon via (TSV) formed therein for electricallyconnecting the firs chip and the second chip.
 2. The semiconductor chipstack of claim 1, wherein the second chip further comprises at least asecond TSV.
 3. The semiconductor chip stack of claim 1, wherein thefirst circuit comprises a core array of the first memory.
 4. Thesemiconductor chip stack of claim 1, wherein the first circuit furthercomprises at least a core array of a second memory.
 5. The semiconductorchip stack of claim 4, wherein the second circuit further compriseslogic circuits, ESD protection devices, and I/O pads respectively of thesecond memory.
 6. The semiconductor chip stack of claim 1 furthercomprising a third chip having a third circuit with a third integrationdensity formed therein.
 7. The semiconductor chip stack of claim 6,wherein the third integration density is larger than the secondintegration density.
 8. The semiconductor chip stack of claim 6, whereinthe third chip further comprises at least a third TSV.
 9. Thesemiconductor chip stack of claim 6, wherein the first circuit and thethird circuit respectively comprise a core array of the first memory anda core array of a third memory, and the first memory is different fromthe third memory.
 10. The semiconductor chip stack of claim 9, whereinthe second circuit further comprises logic circuits, ESD protectiondevices and I/O pads respectively of the third memory.
 11. Thesemiconductor chip stack of claim 6, wherein the first circuit and thethird circuit comprise same memory core arrays.
 12. The semiconductorchip stack of claim 11, wherein the logic circuits, the ESD protectiondevices and the I/O pads of the second circuit are corresponding to thememory core arrays.